[SPARK-7576] [MLLIB] Add spark.ml user guide doc/example for ElementwiseProduct
[SPARK-7576] [MLLIB] Add spark.ml user guide doc/example for ElementwiseProduct

Author: Octavian Geagla <ogeagla@gmail.com>

Closes #6501 from ogeagla/ml-guide-elemwiseprod and squashes the following commits:

4ad93d5 [Octavian Geagla] [SPARK-7576] [MLLIB] Incorporate code review feedback.
f7be7ad [Octavian Geagla] [SPARK-7576] [MLLIB] Add spark.ml user guide doc/example for ElementwiseProduct.

(cherry picked from commit da2112aef28e63c452f592e0abd007141787877d)
Signed-off-by: Joseph K. Bradley <461476587780aa9fa5611ea6dc3912c146a91760@databricks.com>

andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap